A quick sharp blow to the head. It's one of the most humane methods of euthanasia after chemical overdose as if done correctly, it's instant and the fish is dead before its brain processes anything.

I wrap my bettas up in a damp cloth to keep them calm, and then use a hammer. The cloth also makes it a lot less harder to do.

I'm not fond of freezing or of putting tropical fish into iced water to 'shock them to death'. I can see both of these scenarios causing stress and possible pain to your fish as death does not occur instantly.

Because sometimes they arent curable and were 100% sure and they are obviously suffering so instead of letting them sit there suffering we end it. Also some breeders have to kill unwanted/deformed fish from their fry tanks.

Well... you can always ask an older family member to help, you can explain the situation to them, but many people can't bring themselves to let anyone else euthanize their fish either.

If you can't get the clove oil method, and you can't euthanize in any of these methods, do you best to make him as comfortable as possible... clean, warm water, tannins from oak or indian almond leaves, lower water level so he doesn't have to struggle to swim... Make his last few days as comfortable as he can possibly have it so he can pass peacefully in a safe comfortable home..

i was never able to euth my fish, so i made them comfortable and made their suffering(if they were suffering) as minimal as possible. their last few days(or, in Caroline's case, month... poor gal....) was amazing.